Blockchain implementing reliability database

ABSTRACT

An example operation may include one or more of receiving a request for trust information of an off-chain data source from a client, determining a category type of the off-chain data source from among a plurality of category types based on the request, retrieving a reliability value of the off-chain data source linked to one or more of an identity of the off-chain data source and the determined category type from a reliability database implemented via a distributed ledger shared among a plurality of peer nodes, and transmitting the retrieved reliability value linked to the category type to the client.

TECHNICAL FIELD

This application generally relates to a database storage system, andmore particularly, to a decentralized database such as a blockchain inwhich reliability information of external data sources may be storedwithin a database on a blockchain ledger.

BACKGROUND

A centralized database stores and maintains data in one single database(e.g., database server) at one location. This location is often acentral computer, for example, a desktop central processing unit (CPU),a server CPU, or a mainframe computer. Information stored on acentralized database is typically accessible from multiple differentpoints. Multiple users or client workstations can work simultaneously onthe centralized database, for example, based on a client/serverconfiguration. Because of its single location, a centralized database iseasy to manage, maintain, and control, especially for purposes ofsecurity. Within a centralized database data integrity is maximized anddata redundancy is minimized as a single storing place of all data alsoimplies that a given set of data only has one primary record. This aidsin the maintaining of data as accurate and as consistent as possible andenhances data reliability.

However, a centralized database suffers from significant drawbacks. Forexample, a centralized database has a single point of failure. Inparticular, if there is no fault-tolerance setup and a hardware failureoccurs, all data within the database is lost and work of all users isinterrupted. In addition, a centralized database is highly dependent onnetwork connectivity. As a result, the slower the Internet connection,the longer the amount of time needed for each database access. Anotherdrawback is that bottlenecks occur when the centralized databaseexperiences of high traffic due to the single location. Furthermore, acentralized database provides limited access to data because only onecopy of the data is maintained by the database. As a result, multipleusers may not be able to access the same piece of data at the same timewithout creating problems such as overwriting stored data. Furthermore,because a central database system has minimal to no data redundancy, ifa set of data is unexpectedly lost it is difficult to retrieve it otherthan through manual operation from back-up disk storage.

A decentralized database such as a blockchain system provides a storagesystem capable of addressing the drawbacks of a centralized database. Ina blockchain system, multiple peer nodes store a distributed ledgerwhich includes a blockchain. Clients interact with peer nodes to gainaccess to the blockchain. The peer nodes may be controlled by differententities having different interests and therefore are not trustingentities with respect to one another. Furthermore, there is no centralauthority in a blockchain. Therefore, in order for data to be added toor changed on the distributed ledger in a trusted manner, a consensus ofpeer nodes must occur. The consensus provides a way for trust to beachieved in a blockchain system of untrusting peer nodes.

Transactions which are performed via a blockchain between parties mayrequire data from an external source (e.g., stocks, medical information,property information, documents, and the like). At present, it isdifficult for a blockchain to verify that the external source or thedata provided from the external source is reliable. In other words, theblockchain typically “takes the word” of the external data source. Also,external sources may have a reliability that changes over time. Forexample, an external source may be reliable during a first period oftime, but may become unreliable when the data source is compromised by ahacker or other malicious party. Accordingly, what is needed is amechanism for keeping and updating a reliability of an external datasource.

SUMMARY

One example embodiment may provide a system that includes one or more ofa network interface configured to receive a request for trustinformation of an off-chain data source from a client, and a processorconfigured to one or more of determine a category type of the off-chaindata source from among a plurality of category types based on therequest, and retrieve a reliability value of the off-chain data sourcelinked to one or more of an identity of the off-chain data source andthe determined category type from a reliability database implemented viaa distributed ledger shared among a plurality of peer nodes, wherein theprocessor may be further configured to control the network interface totransmit the retrieved reliability value linked to the category type tothe client.

Another example embodiment may provide a method that includes one ormore of receiving a request for trust information of an off-chain datasource from a client, determining a category type of the off-chain datasource from among a plurality of category types based on the request,retrieving a reliability value of the off-chain data source linked toone or more of an identity of the off-chain data source and thedetermined category type from a reliability database implemented via adistributed ledger shared among a plurality of peer nodes, andtransmitting the retrieved reliability value linked to the category typeto the client.

Another example embodiment may provide a system that includes one ormore of a network interface to receive a reliability value of anoff-chain data source, and a processor to attempt to identify a categorytype of the reliability value of the off-chain data source from among aplurality of category types, determine whether an agreement on thereceived reliability value has been reached among a plurality of peernodes, and, in response to a determination that the agreement has beenreached, store a database entry which includes an identity of theoff-chain data source, the category type if identified, and the agreedupon reliability value within a reliability database on a distributedledger of the plurality of peer nodes.

Another example embodiment may provide a method that includes one ormore of receiving a reliability value of an off-chain data source,attempting to identify a category type of the reliability value of theoff-chain data source from among a plurality of category types,determining whether an agreement on the received reliability value hasbeen reached among a plurality of peer nodes, and in response to adetermination that the agreement has been reached, storing a databaseentry which includes an identity of the off-chain data source, thecategory type if identified, and the agreed upon reliability valuewithin a reliability database on a distributed ledger of the pluralityof peer nodes.

A further example embodiment may provide a non-transitory computerreadable medium comprising instructions, that when read by a processor,cause the processor to perform one or more of receiving a reliabilityvalue of an off-chain data source, attempting to identify a categorytype of the reliability value of the off-chain data source from among aplurality of category types, determining whether an agreement on thereceived reliability value has been reached among a plurality of peernodes, and in response to a determination that the agreement has beenreached, storing a database entry which includes an identity of theoff-chain data source, the category type if identified, and the agreedupon reliability value within a reliability database on a distributedledger of the plurality of peer nodes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating of a blockchain network implementing areliability database, according to example embodiments.

FIG. 2A is a diagram illustrating a peer node blockchain architectureconfiguration for an asset sharing scenario, according to exampleembodiments.

FIG. 2B is a diagram illustrating a peer node blockchain configuration,according to example embodiments.

FIG. 3 is a diagram illustrating a permissioned blockchain network,according to example embodiments.

FIG. 4A is a diagram illustrating a process of a blockchain peer noderetrieving reliability data, according to example embodiments.

FIG. 4B is a diagram illustrating a recursive data structure storingreliability data, according to example embodiments.

FIG. 5A is a diagram illustrating a method of storing reliability dataof an external data source on a distributed ledger, according to exampleembodiments.

FIG. 5B is a diagram illustrating a method of retrieving reliabilitydata of an external data source from a distributed ledger, according toexample embodiments.

FIG. 5C is a diagram illustrating a method of storing modifications inreliability of an external data source via a blockchain, according toexample embodiments.

FIG. 5D is a diagram illustrating a method of storing a snapshot of adatabase via a blockchain, according to example embodiments.

FIG. 5E is a diagram illustrating a method of determining reliability ofan external data source based on recursively retrieved data, accordingto example embodiments.

FIG. 5F is a diagram illustrating a method of proactively updatingreliability data of an external data source, according to exampleembodiments.

FIG. 6A is a diagram illustrating a physical infrastructure configuredto perform various operations on the blockchain in accordance with oneor more operations described herein, according to example embodiments.

FIG. 6B is a diagram illustrating a smart contract configuration amongcontracting parties and a mediating server configured to enforce smartcontract terms on a blockchain, according to example embodiments.

FIG. 6C is a diagram illustrating a smart contract configuration amongcontracting parties and a mediating server configured to enforce thesmart contract terms on the blockchain according to example embodiments.

FIG. 6D is a diagram illustrating another example blockchain-based smartcontact system, according to example embodiments.

FIG. 7A is a diagram illustrating a process of a new block being addedto a blockchain ledger, according to example embodiments.

FIG. 7B is a diagram illustrating contents of a data block structure forblockchain, according to example embodiments.

FIG. 8 is a diagram illustrating an example computer system configuredto support one or more of the example embodiments.

DETAILED DESCRIPTION

It will be readily understood that the instant components, as generallydescribed and illustrated in the figures herein, may be arranged anddesigned in a wide variety of different configurations. Thus, thefollowing detailed description of the embodiments of at least one of amethod, apparatus, non-transitory computer readable medium and system,as represented in the attached figures, is not intended to limit thescope of the application as claimed but is merely representative ofselected embodiments.

The instant features, structures, or characteristics as describedthroughout this specification may be combined in any suitable manner inone or more embodiments. For example, the usage of the phrases “exampleembodiments”, “some embodiments”, or other similar language, throughoutthis specification refers to the fact that a particular feature,structure, or characteristic described in connection with the embodimentmay be included in at least one embodiment. Thus, appearances of thephrases “example embodiments”, “in some embodiments”, “in otherembodiments”, or other similar language, throughout this specificationdo not necessarily all refer to the same group of embodiments, and thedescribed features, structures, or characteristics may be combined inany suitable manner in one or more embodiments.

In addition, while the term “message” may have been used in thedescription of embodiments, the application may be applied to many typesof network data, such as, packet, frame, datagram, etc. The term“message” also includes packet, frame, datagram, and any equivalentsthereof. Furthermore, while certain types of messages and signaling maybe depicted in exemplary embodiments they are not limited to a certaintype of message, and the application is not limited to a certain type ofsignaling.

Example embodiments provide methods, systems, non-transitory computerreadable media, devices, and/or networks, which provide a blockchainnetwork which implements a database via a distributed ledger for storingand tracking changes to reliability of external data sources. Externaldata sources often provide data that is relied on when conductingtransactions or other storage on a blockchain. For example, two partiesmay rely on a stock price, an insurance report, a medical file, anappraisal, and the like, from an external data source. External datasources can include organizations, enterprises, groups, individuals,software applications, systems, and the like. Prior to the exampleembodiments, it was difficult to attribute trust to external datasources and therefore these sources were taken as valid. The exampleembodiments provide a mechanism for assigning a trust (reliabilityvalue) to external data and/or an external data source. The reliabilityinformation can be stored in a reliability database within a distributedledger that is shared among a plurality of blockchain peer nodes.Furthermore, changes in reliability of the external data source can betracked through a blockchain on the distributed ledger.

A decentralized database is a distributed storage system which includesmultiple nodes that communicate with each other. A blockchain is anexample of a decentralized database which includes an append-onlyimmutable data structure resembling a distributed ledger capable ofmaintaining records between mutually untrusted parties. The untrustedparties are referred to herein as peers or peer nodes. Each peermaintains a copy of the database records and no single peer can modifythe database records without a consensus being reached among thedistributed peers. For example, the peers may execute a consensusprotocol to validate blockchain storage transactions, group the storagetransactions into blocks, and build a hash chain over the blocks. Thisprocess forms the ledger by ordering the storage transactions, as isnecessary, for consistency. In a public or permission-less blockchain,anyone can participate without a specific identity. Public blockchainsoften involve native cryptocurrency and use consensus based on a proofof work (PoW). On the other hand, a permissioned blockchain databaseprovides a system which can secure inter-actions among a group ofentities which share a common goal but which do not fully trust oneanother, such as businesses that exchange funds, goods, information, andthe like.

A blockchain operates arbitrary, programmable logic tailored to adecentralized storage scheme and referred to as “smart contracts” or“chaincodes.” In some cases, specialized chaincodes may exist formanagement functions and parameters which are referred to as systemchaincode. Smart contracts are trusted distributed applications whichleverage tamper-proof properties of the blockchain database and anunderlying agreement between nodes which is referred to as anendorsement or endorsement policy. In general, blockchain transactionstypically must be “endorsed” before being committed to the blockchainwhile transactions which are not endorsed are disregarded. A typicalendorsement policy allows chaincode to specify endorsers for atransaction in the form of a set of peer nodes that are necessary forendorsement. When a client sends the transaction to the peers specifiedin the endorsement policy, the transaction is executed to validate thetransaction. After validation, the transactions enter an ordering phasein which a consensus protocol is used to produce an ordered sequence ofendorsed transactions grouped into blocks.

Nodes are the communication entities of the blockchain system. A “node”may perform a logical function in the sense that multiple nodes ofdifferent types can run on the same physical server. Nodes are groupedin trust domains and are associated with logical entities that controlthem in various ways. Nodes may include different types, such as aclient or submitting-client node which submits a transaction-invocationto an endorser (e.g., peer), and broadcasts transaction-proposals to anordering service (e.g., ordering node). Another type of node is a peernode which can receive client submitted transactions, commit thetransactions and maintain a state and a copy of the ledger of blockchaintransactions. Peers can also have the role of an endorser, although itis not a requirement. An ordering-service-node or orderer is a noderunning the communication service for all nodes, and which implements adelivery guarantee, such as a broadcast to each of the peer nodes in thesystem when committing transactions and modifying a world state of theblockchain, which is another name for the initial blockchain transactionwhich normally includes control and setup information.

A ledger is a sequenced, tamper-resistant record of all statetransitions of a blockchain. State transitions may result from chaincodeinvocations (i.e., transactions) submitted by participating parties(e.g., client nodes, ordering nodes, endorser nodes, peer nodes, etc.).A transaction may result in a set of asset key-value pairs beingcommitted to the ledger as one or more operands, such as creates,updates, deletes, and the like. The ledger includes a blockchain (alsoreferred to as a chain) which is used to store an immutable, sequencedrecord in blocks. The ledger also includes a state database whichmaintains a current state of the blockchain. There is typically oneledger per channel. Each peer node maintains a copy of the ledger foreach channel of which they are a member.

A chain is a transaction log which is structured as hash-linked blocks,and each block contains a sequence of N transactions where N is equal toor greater than one. The block header includes a hash of the block'stransactions, as well as a hash of the prior block's header. In thisway, all transactions on the ledger may be sequenced andcryptographically linked together. Accordingly, it is not possible totamper with the ledger data without breaking the hash links. A hash of amost recently added blockchain block represents every transaction on thechain that has come before it, making it possible to ensure that allpeer nodes are in a consistent and trusted state. The chain may bestored on a peer node file system (i.e., local, attached storage, cloud,etc.), efficiently supporting the append-only nature of the blockchainworkload.

The current state of the immutable ledger represents the latest valuesfor all keys that are included in the chain transaction log. Because thecurrent state represents the latest key values known to a channel, it issometimes referred to as a world state. Chaincode invocations executetransactions against the current state data of the ledger. To make thesechaincode interactions efficient, the latest values of the keys may bestored in a state database. The state database may be simply an indexedview into the chain's transaction log, it can therefore be regeneratedfrom the chain at any time. The state database may automatically berecovered (or generated if needed) upon peer node startup, and beforetransactions are accepted.

External data is often used as a factor in execution of transactions andother requests via a blockchain. For example, at a time oft contract,the transaction conditions such as an amount may be decided based ondata provided by a third party. This is just one example of an externaldata provider. Other examples include, but are not limited to, stocks,insurance, medical information, financial data, weather, and the like.However, it is possible that the data from the data provider and/or thedata provider itself is not reliable. Furthermore, the reliability maychange over time due to various factors such as malicious attack,improved calculations, better sensors, and the like. Therefore, it maybe desirable for a client transacting on a blockchain to know areliability of the external data source before they conduct business onthe blockchain.

The example embodiments overcome these drawbacks by providing a servicethat can determine a reliability of an external data source based onhistorical dealings or other factors. Furthermore, the service can beused by blockchain peer nodes to keep and track reliability data of theexternal data sources providing data to a blockchain shared among thepeer nodes. Each peer node may store a reliability database that isimplemented within a distributed ledger that includes the blockchain.Accordingly, the reliability database may be managed on-chain. Withinthe reliability database, the peer node may store and proactively updatereliability values that are received from the reliability service. Insome cases, the reliability data from the reliability service may bedetermined recursively from other entities when there is no directreliability value for an external data source.

Some benefits of the instant solutions described and depicted hereininclude an improvement to the trust of a blockchain network thereforepreventing improper transactions and fraud from occurring on theblockchain. In doing so, the system creates a more reliabilityblockchain system that can be trusted. Furthermore, changes inreliability value can be tracked on a blockchain and only committed tothe blockchain when a consensus has been received from the peer nodes ofthe blockchain.

Blockchain is different from a traditional database in that blockchainis not a central storage but rather a decentralized, immutable, andsecure storage, where nodes must share in changes to records in thestorage. Some properties that are inherent in blockchain and which helpimplement the blockchain include, but are not limited to, an immutableledger, smart contracts, security, privacy, decentralization, consensus,endorsement, accessibility, and the like, which are further describedherein. According to various aspects, the decentralized and distributednature of the blockchain along with the consensus ensures that thereliability of an external data source is fairly and adequately trackedby the blockchain network as a whole, and not just a central authoritywhich is susceptible to fraud or mistake.

In some embodiments, each peer may determine a reliability of inputteddata. Furthermore, the blockchain network may determine a finalreliability based on consensus (agreement) with all of other peers thatalso calculate a reliability of the inputted data. The consensus methodmay be pre-defined between the peer nodes, for example, average, median,maximum, minimum, etc. Furthermore, changes to the reliability data maybe received from the service and they may be propagated through theblockchain network after a consensus has been reached. The changes maybe recorded within a blockchain thereby keeping a historical chain ofreliability for an external data source on the immutable ledger.

The example embodiments also change how data may be stored within ablock structure of the blockchain. For example, a data block may includeinformation about the reliability of an external data source which maybe stored within a data segment of the data block. By storingreliability information of an external data source within data blocks ofa blockchain, the reliability as well as any changes in reliability maybe appended to an immutable ledger through a hash-linked chain ofblocks. Thus, a chain of reliability may be recorded within theimmutable ledger and accessed by nodes of the blockchain.

FIG. 1 illustrates a blockchain network 100 implementing a reliabilitydatabase within a distributed ledger, according to example embodiments.Referring to FIG. 1, the blockchain network 100 includes a plurality ofpeer nodes 120-123 and an ordering node 130 which communicate via anetwork 140 such as the Internet, a private network, and/or the like.Here, the peer nodes 120-123 may correspond to different untrustingentities, but embodiments are not limited thereto. Each peer node120-123 may be capable of acting as a submitting node (client node) forsubmitting transactions for storage on a blockchain. The blockchain maybe stored within a distributed ledger which is replicated among all ofthe peer nodes 120-123. Each of the peer nodes 120-123 may also becapable of acting as an endorsing node.

In the example of FIG. 1, a client 110 submits a transaction request topeer node 122 for execution and storage within the blockchain managed bythe blockchain network 100. The transaction may be forwarded toendorsing peer nodes which may be predefined by one or more endorsementpolicies. In some cases, prior to submitting the transaction request topeer node 122, the client 110 may want information on an external datasource that is to provide data that will be used for the transaction.Each of the peer nodes 120-123 may store a respective reliabilitydatabase 120A-123A within a distributed ledger that is replicated andshared among the peer node 120-123. The reliability database 120A-123Amay store reliability information of an external data source and/or theexternal data by category type from among a plurality of category typesof data. The reliability information may be provided from a trustedservice that is chosen by the peer nodes 120-123 in advance. In someembodiments, the reliability database 120A-123A may be implementedwithin a state database of the distributed ledger or some other keyvalue store (KVS) which records attributes of reliability of an externaldata source which may include one or more of an organization ID of theexternal data source, a category type of the external data, a timestampof the reliability determination, and a reliability value.

In response to receiving a reliability request from the client 110, thepeer node 122 may access the reliability database 122A to retrievereliability information of an external data source and/or its data to beprovided to the transaction. In some embodiments, the external data maybe further managed based on categories. In other words, the reliabilitymay be further refined into specific categories of data types. Forexample, an external data source may have a different reliability valuefor stocks versus medical data, etc. The reliability informationretrieved from the reliability database 122A may be transmitted from thepeer node 122 to the client 110. In response, the client 110 maydetermine whether or not to conduct the blockchain transaction.

FIG. 2A illustrates a blockchain architecture configuration 200,according to example embodiments. Referring to FIG. 2A, the blockchainarchitecture 200 may include certain blockchain elements, for example, agroup of blockchain nodes 202. The blockchain nodes 202 may include oneor more nodes 204-210 (these four nodes are depicted by example only).These nodes participate in a number of activities, such as blockchaintransaction addition and validation process (consensus). One or more ofthe blockchain nodes 204-210 may endorse transactions based onendorsement policy and may provide an ordering service for allblockchain nodes in the architecture 200. A blockchain node may initiatea blockchain authentication and seek to write to a blockchain immutableledger stored in blockchain layer 216, a copy of which may also bestored on the underpinning physical infrastructure 214. The blockchainconfiguration may include one or more applications 224 which are linkedto application programming interfaces (APIs) 222 to access and executestored program/application code 220 (e.g., chaincode, smart contracts,etc.) which can be created according to a customized configurationsought by participants and can maintain their own state, control theirown assets, and receive external information. This can be deployed as atransaction and installed, via appending to the distributed ledger, onall blockchain nodes 204-210.

The blockchain base or platform 212 may include various layers ofblockchain data, services (e.g., cryptographic trust services, virtualexecution environment, etc.), and underpinning physical computerinfrastructure that may be used to receive and store new transactionsand provide access to auditors which are seeking to access data entries.The blockchain layer 216 may expose an interface that provides access tothe virtual execution environment necessary to process the program codeand engage the physical infrastructure 214. Cryptographic trust services218 may be used to verify transactions such as asset exchangetransactions and keep information private.

The blockchain architecture configuration of FIG. 2A may process andexecute program/application code 220 via one or more interfaces exposed,and services provided, by blockchain platform 212. The code 220 maycontrol blockchain assets. For example, the code 220 can store andtransfer data, and may be executed by nodes 204-210 in the form of asmart contract and associated chaincode with conditions or other codeelements subject to its execution. As a non-limiting example, smartcontracts may be created to execute reminders, updates, and/or othernotifications subject to the changes, updates, etc. The smart contractscan themselves be used to identify rules associated with authorizationand access requirements and usage of the ledger. Also, the smartcontracts can be used to store and update reliability data of externaldata sources within a reliability database on the distributed ledger.For example, the read set 226 may be processed by one or more processingentities (e.g., virtual machines) included in the blockchain layer 216.The write set 228 may include changes to key values. The physicalinfrastructure 214 may be utilized to retrieve any of the data orinformation described herein.

Within chaincode, a smart contract may be created via a high-levelapplication and programming language, and then written to a block in theblockchain. The smart contract may include executable code which isregistered, stored, and/or replicated with a blockchain (e.g.,distributed network of blockchain peers). A transaction is an executionof the smart contract code which can be performed in response toconditions associated with the smart contract being satisfied. Theexecuting of the smart contract may trigger a trusted modification(s) toa state of a digital blockchain ledger. The modification(s) to theblockchain ledger caused by the smart contract execution may beautomatically replicated throughout the distributed network ofblockchain peers through one or more consensus protocols.

The smart contract may write data to the blockchain in the format ofkey-value pairs. Furthermore, the smart contract code can read thevalues stored in a blockchain and use them in application operations.The smart contract code can write the output of various logic operationsinto the blockchain. The code may be used to create a temporary datastructure in a virtual machine or other computing platform. Data writtento the blockchain can be public and/or can be encrypted and maintainedas private. The temporary data that is used/generated by the smartcontract is held in memory by the supplied execution environment, thendeleted once the data needed for the blockchain is identified.

A chaincode may include the code interpretation of a smart contract,with additional features. As described herein, the chaincode may beprogram code deployed on a computing network, where it is executed andvalidated by chain validators together during a consensus process. Thechaincode receives a hash and retrieves from the blockchain a hashassociated with the data template created by use of a previously storedfeature extractor. If the hashes of the hash identifier and the hashcreated from the stored identifier template data match, then thechaincode sends an authorization key to the requested service. Thechaincode may write to the blockchain data associated with thecryptographic details.

FIG. 2B illustrates an example of a transactional flow 250 between nodesof the blockchain in accordance with an example embodiment. Referring toFIG. 2B, the transaction flow may include a transaction proposal 291sent by an application client node 260 to an endorsing peer node 281.The endorsing peer 281 may verify the client signature and execute achaincode function to initiate the transaction. The output may includethe chaincode results, a set of key/value versions that were read in thechaincode (read set), and the set of keys/values that were written inchaincode (write set). The proposal response 292 is sent back to theclient 260 along with an endorsement signature, if approved. The client260 assembles the endorsements into a transaction payload 293 andbroadcasts it to an ordering service node 284. The ordering service node284 then delivers ordered transactions as blocks to all peers 281-283 ona channel. Before committal to the blockchain, each peer 281-283 mayvalidate the transaction. For example, the peers may check theendorsement policy to ensure that the correct allotment of the specifiedpeers have signed the results and authenticated the signatures againstthe transaction payload 293.

The client node 260 may initiate the transaction 291 by constructing andsending a request to the peer node 281, which is an endorser. There maybe more than one endorser, but one is shown here for convenience. Theclient 260 may include an application that leverages a supportedsoftware development kit (SDK), such as NODE, JAVA, PYTHON, and thelike, which utilizes an available API to generate a transactionproposal. The transaction proposal 291 is a request to invoke achaincode function so that data can be read and/or written to the ledger(i.e., write new key value pairs for the assets). The SDK may serve as ashim to package the transaction proposal into a properly architectedformat (e.g., protocol buffer over a remote procedure call (RPC)) andtake the client's cryptographic credentials to produce a uniquesignature for the transaction proposal.

In response, the endorsing peer node 281 may verify (a) that thetransaction proposal is well formed, (b) the transaction has not beensubmitted already in the past (replay-attack protection), (c) thesignature is valid, and (d) that the submitter (client 260, in theexample) is properly authorized to perform the proposed operation onthat channel. The endorsing peer node 281 may take the transactionproposal inputs as arguments to the invoked chaincode function. Thechaincode is then executed against a current state database to producetransaction results including a response value, read set, and write set.However, no updates are made to the ledger at this point. In 292, theset of values, along with the endorsing peer node's 281 signature ispassed back as a proposal response 292 to the SDK of the client 260which parses the payload for the application to consume.

In response, the application of the client 260 inspects/verifies theendorsing peers signatures and compares the proposal responses todetermine if the proposal response is the same. If the chaincode onlyqueried the ledger, the application would inspect the query response andwould typically not submit the transaction to the ordering node service284. If the client application intends to submit the transaction to theordering node service 284 to update the ledger, the applicationdetermines if the specified endorsement policy has been fulfilled beforesubmitting (i.e., did all peer nodes necessary for the transactionendorse the transaction). Here, the client may include only one ofmultiple parties to the transaction. In this case, each client may havetheir own endorsing node, and each endorsing node will need to endorsethe transaction. The architecture is such that even if an applicationselects not to inspect responses or otherwise forwards an unendorsedtransaction, the endorsement policy will still be enforced by peers andupheld at the commit validation phase.

After successful inspection, in step 293 the client 260 assemblesendorsements into a transaction and broadcasts the transaction proposaland response within a transaction message to the ordering node 284. Thetransaction may contain the read/write sets, the endorsing peerssignatures and a channel ID, as well as the timestamp information andreliability information described herein. The ordering node 284 does notneed to inspect the entire content of a transaction in order to performits operation, instead the ordering node 284 may simply receivetransactions from all channels in the network, order themchronologically by channel, and create blocks of transactions perchannel.

The blocks of the transaction are delivered from the ordering node 284to all peer nodes 281-283 on the channel. The transactions 294 withinthe block are validated to ensure any endorsement policy is fulfilledand to ensure that there have been no changes to ledger state for readset variables since the read set was generated by the transactionexecution. Transactions in the block are tagged as being valid orinvalid. Furthermore, in step 295 each peer node 281-283 appends theblock to the channel's chain, and for each valid transaction the writesets are committed to current state database. An event is emitted, tonotify the client application that the transaction (invocation) has beenimmutably appended to the chain, as well as to notify whether thetransaction was validated or invalidated.

FIG. 3 illustrates an example of a permissioned blockchain network 300,which features a distributed, decentralized peer-to-peer architecture,and a certificate authority 318 managing user roles and permissions. Inthis example, the blockchain user 302 may submit a transaction to thepermissioned blockchain network 310. In this example, the transactioncan be a deploy, invoke or query, and may be issued through aclient-side application leveraging an SDK, directly through a REST API,or the like. Trusted business networks may provide access to regulatorsystems 314, such as auditors (the Securities and Exchange Commission ina U.S. equities market, for example). Meanwhile, a blockchain networkoperator system of nodes 308 manage member permissions, such asenrolling the regulator system 310 as an “auditor” and the blockchainuser 302 as a “client.” An auditor could be restricted only to queryingthe ledger whereas a client could be authorized to deploy, invoke, andquery certain types of chaincode.

A blockchain developer system 316 writes chaincode and client-sideapplications. The blockchain developer system 316 can deploy chaincodedirectly to the network through a REST interface. To include credentialsfrom a traditional data source 330 in chaincode, the developer system316 could use an out-of-band connection to access the data. In thisexample, the blockchain user 302 connects to the network through a peernode 312. Before proceeding with any transactions, the peer node 312retrieves the user's enrollment and transaction certificates from thecertificate authority 318. In some cases, blockchain users must possessthese digital certificates in order to transact on the permissionedblockchain network 310. Meanwhile, a user attempting to drive chaincodemay be required to verify their credentials on the traditional datasource 330. To confirm the user's authorization, chaincode can use anout-of-band connection to this data through a traditional processingplatform 320.

FIG. 4A illustrates a process 400 of a blockchain peer node 420retrieving reliability data, according to example embodiments. Forexample, the process 400 may be implemented by chaincode executing onthe blockchain peer node 420. In this example, the peer node 420 mayperform various steps. In a first step, the peer node 420 may receive arequest from a client 410 for reliability information of an externaldata source. In response, the peer node 420 may attempt to retrieve thereliability data from a key value store 424 that is implemented within adistributed ledger 422. Here, the peer node 420 may be a member of ablockchain network that includes a plurality of peer nodes, and eachpeer node may store a replica of the key value store 424 which may beused as a reliability database.

The peer node 420 may maintain one or more attributes 426 for eachexternal data source in the reliability database (KVS 424, in thisexample). Examples of the attributes 426 include an ID of the externaldata source such as an organization ID, an enterprise ID, an individualID, a group ID, and the like. Other attributes 426 may include a datacategory type of the external data source/reliability, a reliabilityvalue, and a timestamp at which the reliability value was added to theKVS 424. In some embodiments, an external data source may have multiplereliability values for multiple data categories. Therefore, the requestfrom the client 410 may include an identification of the category ofdata from among a plurality of possible categories. The KVS 424 maystore the most current state of the reliability information for anexternal data source. In some embodiments, the KVS 424 may beimplemented within a world state database of the distributed ledger 422,but embodiments are not limited thereto.

When a peer node 420 is able to find a reliability value for theexternal data source within the KVS 424, the peer node 420 may providethe reliability value to other peer nodes (or an ordering node) forconsensus. In addition, the other peer nodes may retrieve theirreliability values for the external data source, come to an agreement onthe reliability value, and provide the agreed reliability value to theclient. Here, the agreed upon reliability value may be reached based ona combination of the reliability values retrieved from the reliabilitydatabases of each of the peer nodes. These values may be different.Therefore, the agreed upon reliability value may be a combination or anaverage of these values from all peer nodes or at least those nodes thathave a reliability value stored therein.

If the peer node 420 is unable to find a reliability value for therequested external data source within the KVS 424, the peer node 420 mayretrieve a reliability value for the external data source from areliability service 430. The reliability service 430 may be agreed uponby peer nodes among the blockchain network at a time of setting up theblockchain or subsequently. The reliability service 430 may store trustinformation, reliability scores, and the like, of organizations that areinvolved with the blockchain network. For example, the reliabilityservice 430 may store trust information within a recursive treestructure 431 such as shown in FIG. 4B. In this example, reliabilitydata of an external data source 432 may be stored as a parent node.

However, if no express reliability value is currently stored for thedata source 432, the reliability service 430 may determine a reliabilityvalue from other organizations that refer or that evaluate thereliability of the external data source 432. These other organizationsmay be other organizations that are identified from the KVS 424 ashaving a reference to the external data source or otherwise deal withthe external data source 432 in the past. As another example, theseorganizations may have other relationships with the external data sourcesuch as intermediate business dealings, expert opinions, and the like,which are not identified from the KVS 424. Accordingly, the reliabilityservice 430 can attempt to find reliability information from a firstlevel of the recursive tree structure 431 based on pointers 434indicating which organizations refer to the reliability of the externaldata source 432.

In some embodiments, the reliability service 430 may recursively movefrom level to level within the tree structure to identify a chain ofreliability data based on levels of referral. For example, the secondlevel of organizations in the recursive data structure 431 may notevaluate the trust of the external data source 432, but instead mayevaluate the reliability of the organizations that directly evaluate thereliability of the external data source 432. This recursive process cancontinue to the third level, a fourth level (not shown), and so on untila predetermined limit of recursive levels has been reached. Accordingly,a chain of reliability can be retrieved based on intermediaterelationships with the external data source. To generate the finalreliability value, the reliability service 430 may use a combination ofthe recursively retrieved reliability information (e.g., scores,ratings, etc.). For example, an average value, a median value, a maximumvalue, a minimum value, and the like, may be used to determine the finalreliability value. As another example, a weighted combination of valuesmay be used where the reliability data gathered higher in the recursivetree structure 431 is given greater weight that the reliability datagathered lower in the recursive tree structure 431. Trust informationfrom the other organizations may be recursively gathered by the service430 from various sources such as social networks, evaluation of experts,actual value of sales and/or its increase/decrease, management state,and so on. These are just examples and the example embodiments are notlimited thereto.

Referring again to FIG. 4A, the reliability service 430 can provide therequested reliability value to the peer node 420. As another example,the reliability service 430 may periodically send updates (orproactively receive requests for updates) of reliability values to thepeer node 420. In this way, the peer node 420 may proactively update thereliability values stored therein on a continuous basis and without arequest from the client 410. Based on a reliability value received fromthe reliability service 430, the peer node 420 may provide thereliability value to the client 410. For example, when the peer node 420determines that a consensus on the reliability value retrieved from thereliability service 430 has been agreed upon by the peer nodes of theblockchain network, the peer node 420 may provide the reliability valueto the client 410. Here, the consensus may be determined when anendorsement policy has been satisfied for changes to the reliabilityvalue to be stored in the KVS 424. In other words, before a reliabilityvalue can be stored or modified within the KVS 424, a consensus of peernodes may be required to endorse the change. The endorsement may beperformed by the peer nodes signing the modification. Furthermore, therecursive tree structure 431 allows the service 430 to look for othercompanies (parties) that evaluate the external data source. If the“other companies” do not exist in the reliability database, the servicemay further look for other companies that evaluate the other companies.This process may be performed recursively.

In response to a change in the reliability database (KVS 424) such asthe storage of a reliability value of an external data source for thefirst time, or an update to a previously stored reliability value of theexternal data source, a transaction may be stored in blockchain 428 thatis also on the distributed ledger 422. The transaction may identify theexternal data source, the modification to the reliability (e.g., new,modified, deleted, etc.) and a timestamp at which the change occurred.In some embodiments, the peer node 420 may capture a snapshot of thereliability database (e.g., the KVS 424) including the current values ofreliability for one or more external data sources, and store thesnapshot within the blockchain 428. The snapshot may comprise a key, areliability value identified by the key, and a timestamp, for eachexternal data source and category combination. If the reliability valueis a general reliability for the external data source withoutrestriction on category, the category information may be null. In someembodiments, the modification of the reliability such as the snapshot orthe like, may be hashed prior to storing the data within the blockchain428.

By updating the blockchain 428 to include all changes to a reliabilityvalue for an external data source, a trail of changes to the reliabilityvalue may be stored immutably on the blockchain 428 and accessed byauditors and other interested parties.

As will be appreciated, each peer in a blockchain may store areliability database regarding the reliability of an external datasource, as (source, category) pair, which is initialized at theblockchain peer with the support of a trustable research company or thelike and is agreed by the peers. When a request for reliability data ofthe external data source is received from a client, the peer nodes mayretrieve their reliability values for the external data source, come toan agreement on the reliability value, and provide the agreedreliability value to the client.

Furthermore, the reliability database may be updated (i.e. added withupdated timestamp and reliability values) after agreement when somereliability values are updated at external parties and/or through thetransaction, and all the peers are synchronized on the data in thereliability database. When there is a request for reliability evaluationof the external data source (for a specific category) from a client orother third party, if the reliability data of the external data sourceis in the reliability database, the blockchain peer node may use it.

However, if reliability is not within the reliability database, the peernode may request the trusted reliability service to recursively identifya reliability of the external data source based on organizations orgroups that evaluate the external data source, recursively, until suchgroups(s) that evaluates the external data source is found. Furthermore,a new reliability value may be provided from the service and added orotherwise recorded in reliability database. In some embodiments, thepeer node may go to the trusted reliability service to get the newreliability data proactively without request from a client. This may bedone periodically, randomly, or the like.

According to various embodiments, a client can get the reliability valueof the data or data source that they want to evaluate, even if it's notin the reliability DB. Here, a peer node may recursively determine thereliability value based on external sources (e.g., organizations) thathave some sort of relationship with the data source. The reliabilitydata within the reliability DB may include the reliability value with(source, data category, timestamp, reliability value, etc.) format,where “source” may be a name of a company or a group. When the categorytype is found with its source, the reliability data for that (source,category) pair in the DB is returned to the client. However, datacategory is not mandatory, since some data may just have its source butnot category, like (organization name, null, 2018 Sep. 11, 0.5). In thiscase, for the request from the client, if just the source is found(category is not found) in the reliability DB, the node may return thereliability data of the source.

Also, for storing reliability of data, data category is not mandatory.For example, the received data source may just include the company namewithout category type. In this case, data category cannot be identified.If the reliability data is updated and the reliability value istransmitted to some clients before, the system may inforn the updatedreliability value to the past clients. When the reliability value is notin the DB, the system may determine the reliability value of an externaldata source from recursively retrieved reliability data. In this step,one of the reliability calculation methods is to put weights on the databased on the depth of the recursion and the reliability of theorganization who provides the reliability data.

FIG. 5A illustrates a method 510 of storing reliability data of anexternal data source on a distributed ledger, according to exampleembodiments. Any of the methods described herein including the method ofFIG. 5A may be performed by a computing system such as the computingsystem 800 shown in FIG. 8, or the like. For example, the computingsystem may be a blockchain peer node, a server, a cloud platform, adatabase, a user device, a combination of devices, and the like.Referring to FIG. 5A, in 511, the method may include receiving areliability value of an off-chain data source. For example, thereliability value may represent a level of trust associated with one ormore of the off-chain data source and a data element provided from theoff-chain data source. The value may simply state “TRUST” or “DO NOTTRUST.” As another example, the reliability value may be a rating thatis somewhere in between a range of values (e.g., between 0 to 1.0, −1.0to 1.0, 0 to 100, etc.) In some embodiments, the reliability value maybe received from a trusted service that is agreed upon by the blockchainnodes in advance. The off-chain data source may be an external system(e.g., hardware, software, etc.) that is not allowed access to thedistributed ledger.

In 512, the method may include attempting to identify a category type ofthe reliability value of the off-chain data source from among aplurality of category types. Category types may include categories ofdata such as financial, medical, insurance, legal, and the like. Thereare many different categories of data, and the embodiments should not beconstrued as limited to any particular category of data. In someembodiments, an external data source may be assigned differentreliability values for different categories of data. In someembodiments, the category type may be null. In other words, there may beno category type for the data. Rather, the reliability may be for allcategories, the external data source in general, and the like.

In 513, the method may include determining whether an agreement on thereceived reliability value has been reached among a plurality of peernodes. For example, the agreement may be a consensus among multiple peernodes of a final reliability value for the external data source. Thefinal reliability value may be based on a combination of reliabilityvalues stored by the peer nodes such as an average, a median, a maximum,a minimum, or the like. In some embodiments, the final reliability valuethat is identified from the determining may be a different reliabilityvalue than the received reliability value.

Furthermore, in response to a determination that the agreement has beenreached, in 514 the method may include storing a database entry whichincludes an identity of the off-chain data source, the category type ifidentified, and the agreed upon reliability value within a reliabilitydatabase on a distributed ledger of the plurality of peer nodes. Forexample, the reliability database may be implemented within a key valuestore on the distributed ledger. In some embodiments, the database entrymay further include a timestamp at which the database entry is added tothe reliability database. In some embodiments, the distributed ledgerwhich implements the reliability database may further include ablockchain shared among the plurality of nodes. In some embodiments, ifthe retrieved reliability value includes an updated reliability value,the method may include transmitting the updated reliability value to oneor more clients to inform them of the updated reliability value.

FIG. 5B illustrates a method 520 of retrieving reliability data of anexternal data source from a distributed ledger, according to exampleembodiments. Referring to FIG. 5B, in 521 the method may includereceiving a request for trust information of an off-chain data sourcefrom a client. For example, the request may be sent to a blockchain peernode prior to a transaction being entered into by the client. In 522,the method may include determining a category type of the off-chain datasource from among a plurality of category types based on the request.

Based on an identification of the off-chain data source and/or thecategory type, in 523 the method may further include retrieving areliability value of the off-chain data source linked to one or more ofan identity of the off-chain data source and the determined categorytype from a reliability database implemented via a distributed ledgershared among a plurality of peer nodes. In some embodiments, thereliability value may be retrieved with only the data source ID(off-chain organization ID, etc.). As another example, when theoff-chain data source has multiple categories of data and multiplereliability values corresponding thereto, the category type may also beused to retrieve the data from the reliability database implemented viathe distributed ledger. As another example, when the determined categorytype is not found but the identity of the data source is found in thereliability database, the method may retrieve the reliability value ofthe off-chain data source linked to the identity of the data source fromthe reliability database. In 524, the method may include transmittingthe retrieved reliability value linked to the category type to theclient.

In some embodiments, the retrieving may include retrieving thereliability value of the off-chain data source from a key value store onthe distributed ledger. In some embodiments, the retrieving may includeidentifying a database entry associated with the off-chain data sourcefrom among a plurality of database entries associated with the off-chaindata source corresponding to a plurality of category types. In someembodiments, the retrieved reliability value indicates a level of trustassociated with one or more of the off-chain data source and a dataelement provided from the off-chain data source. In some embodiments,the distributed ledger which implements the reliability database mayfurther include a blockchain shared among the plurality of nodes.

FIG. 5C illustrates a method 530 of storing modifications in reliabilityof an external data source via a blockchain, according to exampleembodiments. Referring to FIG. 5C, in 531, the method may includereceiving a request to modify a reliability value of an off-chain datasource to generate a modified reliability value. For example, therequest may be received from another peer node, a trusted service, andthe like. The modified reliability value may include storing areliability value of an external data source for a first time. Asanother example, the modified reliability value may include an updatedto a previously stored reliability value associated with the externaldata source. The reliability value may be associated with a categorytype of data from among a plurality of categories.

In 532, the method may include determining whether a consensus on themodified reliability value has been received among a plurality of peernodes. For example, the consensus may occur when enough peer nodes haveendorsed the modification to the reliability value. Here, theendorsement policy may be based on any desired policy that is agreedupon by the peer nodes of the blockchain in advance. In response to adetermination that the consensus has been received, in 533 the methodmay include updating a storage to reflect the modified reliability valueassociated with the off-chain data source, and storing an identificationof the modified reliability value within a block among a hash-linkedchain of blocks on a distributed ledger shared among the plurality ofpeer nodes. In some embodiments, a timestamp may also be stored with themodification in the blockchain to identify a point in time at which themodification occurred.

In some embodiments, the storage may be a reliability databaseimplemented on a state database of the distributed ledger and thehash-linked chain of blocks may be a blockchain stored on thedistributed ledger. In some embodiments, the modified reliability valuemay include a change in trust associated with the off-chain data source.In some embodiments, the identification of the modified reliabilityvalue stored in the block among the hash-linked chain of blocks mayinclude an identification of a difference between the modifiedreliability value of the off-chain data source with respect to apreviously stored reliability value of the off-chain data source. Insome embodiments, the off-chain data source may include a computingsystem that does not have access to the distributed ledger. In someembodiments, the determining whether the consensus has been reached mayinclude determining whether a predetermined amount of the plurality ofpeer nodes have endorsed the modified reliability value. In someembodiments, the method may further include transmitting the modifiedreliability value to one or more clients (nodes, applications, etc.) toinform them of the modified reliability value.

FIG. 5D illustrates a method 540 of storing a snapshot of a database viaa blockchain, according to example embodiments. Referring to FIG. 5D, in541 the method may include storing data of one or more off-chain datasources within a database. For example, the database may be areliability database which is implemented on a distributed ledger. In542, the method may include receiving a notification of a change to thedata of the one or more off-chain data sources stored in the database.The notification may include an indication that a consensus has beenreached with respect to a change in the database. As another example,the notification may be triggered by a request, or the like.

In 543, the method may include capturing a snapshot of the data withinthe database based on the notification, where the snapshot identifies ahistorical state of the data within the database, and in 544, the methodmay include storing the captured snapshot of the data in a block fromamong a hash-linked chain of blocks on a distributed ledger. Thesnapshot may include an image, a file, or the like, which captures alist of current database values within the database. The snapshot may bespecific to a particular type of data, a particular organization, aparticular time period, or the like, although embodiments are notlimited thereto.

In some embodiments, the snapshot captures current key values forreliability of a plurality of off-chain data sources. In someembodiments, the snapshot captures current key values for each of aplurality of category types of data for an off-chain data source. Insome embodiments, the snapshot captures current key values within a keyvalue store stored on the distributed ledger. In some embodiments, themethod may further include hashing the captured snapshot prior tostoring the captured snapshot in the block from among the hash-linkedchain of blocks to protect the snapshot from unauthorized access.

FIG. 5E illustrates a method 550 of determining reliability of anexternal data source based on recursively retrieved data, according toexample embodiments. Referring to FIG. 5E, in 551, the method mayinclude receiving a request for trust information of an off-chain datasource from a client. The request may include a request from a clientthat is about to conduct a transaction on a blockchain based on datafrom the off-chain data source. In 552, the method may include detectingthat the trust information of the off-chain data source is not stored ina distributed ledger shared among a plurality of peer nodes. Forexample, the peer node may determine whether a reliability value of theoff-chain data source is stored within a reliability database stored onthe distributed ledger.

In 553, the method may include retrieving reliability data recursivelyidentified and retrieved from a plurality of external sources havingdifferent reliability information of the off-chain data source. In someembodiments, the reliability data may be recursively identified fromamong the plurality of external sources until a threshold number ofexternal sources has been reached. In 554, the method may includedetermining a reliability value based on a combination of therecursively retrieved reliability data from the plurality of externalsources, and in 555, transmitting the determined reliability value tothe client.

In some embodiments, the method may further include updating areliability database of the distributed ledger to include the determinedreliability value. In some embodiments, the method may further includestoring an identification of the determined reliability value and atimestamp within a data block among a hash-linked chain of data blockson the distributed ledger. In some embodiments, the determinedreliability value may indicate a level of trust associated with one ormore of the off-chain data source and a data element provided from theoff-chain data source. In some embodiments, the determining may includedetermining the final value as an average value of the recursivelyretrieved reliability data from the plurality of external sources. Insome embodiments, the determining may include determining thereliability value after weighting based on a depth of the recursion anda reliability of the external data sources that provided the reliabilitydata

FIG. 5F illustrates a method 560 of proactively updating reliabilitydata of an external data source, according to example embodiments.Referring to FIG. 5F, in 561, the method may include storing an initialreliability value in a distributed ledger based on a combination of therecursively retrieved reliability data from a plurality of sources. Forexample, the recursively retrieved reliability data may be retrieved bya trusted service that identifies relationships of entities to anexternal data source and identifies trust/reliability information in arecursive fashion. For example, if an organization does not have adirect reliability rating for an external data source, the service mayidentify a trust/reliability information of an organization that hasdealings with the external data source or that otherwise evaluates theexternal data source. In this way, trust/reliability information of theexternal data source may be obtained indirectly by retrieving atrust/reliability data of an intermediate organization that in some wayis connected to the external data source such as through previousdealings on the blockchain, a relationship, a referral of some kind, andthe like.

In 562, the method may include proactively requesting updates to thepreviously retrieved reliability data from the plurality of sources. Forexample, the proactively requesting may include transmitting a requestto each of the plurality of sources at predetermined intervals. Forexample, the proactively requesting may include transmitting a requestto each of the plurality of sources randomly. In response to receivingan updated reliability data from one or more sources, in 563 the methodmay include generating an updated reliability value based on the updatedreliability data, and modifying the initial reliability value stored onthe distributed ledger based on the updated reliability value. In someembodiments, the updated reliability value may indicate an updated levelof trust associated with one or more of the off-chain data source and adata element provided from the off-chain data source. In someembodiments, the method further include storing an identification of theupdated reliability value and a timestamp of the update within a datablock among a hash-linked chain of data blocks on the distributedledger.

FIG. 6A illustrates an example physical infrastructure configured toperform various operations on the blockchain in accordance with one ormore of the example methods of operation according to exampleembodiments. Referring to FIG. 6A, the example configuration 600Aincludes a physical infrastructure 610 with a blockchain 620 and a smartcontract 630, which may execute any of the operational steps 612included in any of the example embodiments. The steps/operations 612 mayinclude one or more of the steps described or depicted in one or moreflow diagrams and/or logic diagrams. The steps may represent output orwritten information that is written or read from one or more smartcontracts 630 and/or blockchains 620 that reside on the physicalinfrastructure 610 of a computer system configuration. The data can beoutput from an executed smart contract 630 and/or blockchain 620. Thephysical infrastructure 610 may include one or more computers, servers,processors, memories, and/or wireless communication devices. In someembodiments, the smart contract 630 also referred to as chaincode may beexecuted to retrieve blockchain resource information from a blockchainnotification board.

FIG. 6B illustrates an example smart contract configuration amongcontracting parties and a mediating server configured to enforce thesmart contract terms on the blockchain according to example embodiments.Referring to FIG. 6B, the configuration 650B may represent acommunication session, an asset transfer session or a process orprocedure that is driven by a smart contract 630 which explicitlyidentifies one or more user devices 652 and/or 656. The execution,operations and results of the smart contract execution may be managed bya server 654. Content of the smart contract 630 may require digitalsignatures by one or more of the entities 652 and 656 which are partiesto the smart contract transaction. The results of the smart contractexecution may be written to a blockchain as a blockchain transaction.

FIG. 6C illustrates an example smart contract configuration amongcontracting parties and a mediating server configured to enforce thesmart contract terms on the blockchain according to example embodiments.Referring to FIG. 6C, the configuration 650 may represent acommunication session, an asset transfer session or a process orprocedure that is driven by a smart contract 630 which explicitlyidentifies one or more user devices 652 and/or 656. The execution,operations and results of the smart contract execution may be managed bya server 654. Content of the smart contract 630 may require digitalsignatures by one or more of the entities 652 and 656 which are partiesto the smart contract transaction. The results of the smart contractexecution may be written to a blockchain 620 as a blockchaintransaction. The smart contract 630 resides on the blockchain 620 whichmay reside on one or more computers, servers, processors, memories,and/or wireless communication devices.

FIG. 6D illustrates a common interface for accessing logic and data of ablockchain, according to example embodiments. Referring to the exampleof FIG. 6D, an application programming interface (API) gateway 662provides a common interface for accessing blockchain logic (e.g., smartcontract 630 or other chaincode) and data (e.g., distributed ledger,etc.) In this example, the API gateway 662 is a common interface forperforming transactions (invoke, queries, etc.) on the blockchain byconnecting one or more entities 652 and 656 to a blockchain peer (i.e.,server 654). The server 654 is a blockchain network peer component thatholds a copy of the world state (which may include a KVS) within adistributed ledger allowing clients 652 and 656 to query data on theworld state as well as submit transactions into the blockchain networkwhere, depending on the smart contract 630 and endorsement policy,endorsing peers will run the smart contracts 630.

According to various embodiments, the smart contract 630 of the presentapplication may have different APIs 662 that perform different programsfor storing and retrieving reliability data from a reliability databaseand/or a trusted service. For example, the smart contract 630 mayinclude an API that can receive a request from a client for reliabilityof an external data source, retrieve a reliability value of the externaldata source for a particular category, and output the reliability. Asanother example, the smart contract 630 may include an API that canrequest a reliability value from a trusted service when it determinesthat a reliability value for the external data source is not stored inthe reliability database. As another example, the smart contract 630 mayinclude an API that agrees on a consensus of newly coming trusted dataof the external data source prior to storing the trusted data in thereliability database.

FIG. 7A illustrates a process 700 of a new block 730 being added to adistributed ledger 720, according to example embodiments, and FIG. 7Billustrates contents of a block structure 730 for blockchain, accordingto example embodiments. Referring to FIG. 7A, clients (not shown) maysubmit transactions to blockchain nodes 711, 712, and/or 713. Clientsmay be instructions received from any source to enact activity on theblockchain. As an example, clients may be applications (based on a SDK)that act on behalf of a requester, such as a device, person or entity topropose transactions for the blockchain. The plurality of blockchainpeers (e.g., blockchain nodes 711, 712, and 713) may maintain a state ofthe blockchain network and a copy of the distributed ledger 720.

Different types of blockchain nodes/peers may be present in theblockchain network including endorsing peers which simulate and endorsetransactions proposed by clients and committing peers which verifyendorsements, validate transactions, and commit transactions to thedistributed ledger 720. In this example, the blockchain nodes 711, 712,and 713 may perform the role of endorser node, committer node, or both.

The distributed ledger 720 includes a blockchain 722 which storesimmutable, sequenced records in blocks, and a state database 724(current world state) maintaining a current state (key values) of theblockchain 722. One distributed ledger 720 may exist per channel andeach peer maintains its own copy of the distributed ledger 720 for eachchannel of which they are a member. The blockchain 722 is a transactionlog, structured as hash-linked blocks where each block contains asequence of N transactions. Blocks (e.g., block 730) may include variouscomponents such as shown in FIG. 7B. The linking of the blocks (shown byarrows in FIG. 7A) may be generated by adding a hash of a prior block'sheader within a block header of a current block. In this way, alltransactions on the blockchain 722 are sequenced and cryptographicallylinked together preventing tampering with blockchain data withoutbreaking the hash links. Furthermore, because of the links, the latestblock in the blockchain 722 represents every transaction that has comebefore it. The blockchain 722 may be stored on a peer file system (localor attached storage), which supports an append-only blockchain workload.

The current state of the blockchain 722 and the distributed ledger 720may be stored in the state database 724. Here, the current state datarepresents the latest values for all keys ever included in the chaintransaction log of the blockchain 722. Chaincode invocations executetransactions against the current state in the state database 724. Tomake these chaincode interactions extremely efficient, the latest valuesof all keys may be stored in the state database 724. The state database724 may include an indexed view into the transaction log of theblockchain 722 and can therefore be regenerated from the chain at anytime. The state database 724 may automatically get recovered (orgenerated if needed) upon peer startup, before transactions areaccepted.

Endorsing nodes receive transactions from clients and endorse thetransaction based on simulated results. Endorsing nodes hold smartcontracts which simulate the transaction proposals. The nodes needed toendorse a transaction depends on an endorsement policy which may bespecified within chaincode. An example of an endorsement policy is “themajority of endorsing peers must endorse the transaction.” Differentchannels may have different endorsement policies. Endorsed transactionsare forward by the client application to an ordering service 710.

The ordering service 710 accepts endorsed transactions, orders them intoa block, and delivers the blocks to the committing peers. For example,the ordering service 710 may initiate a new block when a threshold oftransactions has been reached, a timer times out, or another condition.In the example of FIG. 7A, blockchain node 712 is a committing peer thathas received a new data block 730 for storage on blockchain 722.

The ordering service 710 may be made up of a cluster of orderers. Theordering service 710 does not process transactions, smart contracts, ormaintain the shared ledger. Rather, the ordering service 710 may acceptthe endorsed transactions, and specifies the order in which thosetransactions are committed to the distributed ledger 720. Thearchitecture of the blockchain network may be designed such that thespecific implementation of ‘ordering’ (e.g., Solo, Kafka, BFT, etc.)becomes a pluggable component.

Transactions are written to the distributed ledger 720 in a consistentorder. The order of transactions is established to ensure that theupdates to the state database 724 are valid when they are committed tothe network. Unlike a cryptocurrency blockchain system (e.g., Bitcoin,etc.) where ordering occurs through the solving of a cryptographicpuzzle, or mining, in this example the parties of the distributed ledger720 may choose the ordering mechanism that best suits that network suchas chronological ordering.

When the ordering service 710 initializes a new block 730, the new block730 may be broadcast to committing peers (e.g., blockchain nodes 711,712, and 713). In response, each committing peer validates thetransaction within the new block 730 by checking to make sure that theread set and the write set still match the current world state in thestate database 724. Specifically, the committing peer can determinewhether the read data that existed when the endorsers simulated thetransaction is identical to the current world state in the statedatabase 724. When the committing peer validates the transaction, thetransaction is written to the blockchain 722 on the distributed ledger720, and the state database 724 is updated with the write data from theread-write set. If a transaction fails, that is, if the committing peerfinds that the read-write set does not match the current world state inthe state database 724, the transaction ordered into a block will stillbe included in that block, but it will be marked as invalid, and thestate database 724 will not be updated.

Referring to FIG. 7B, a block 730 (also referred to as a data block)that is stored on the blockchain 722 of the distributed ledger 720 mayinclude multiple data segments such as a block header 732, block data734, and block metadata 736. It should be appreciated that the variousdepicted blocks and their contents, such as block 730 and its contentsshown in FIG. 7B are merely for purposes of example and are not meant tolimit the scope of the example embodiments. In some cases, both theblock header 732 and the block metadata 736 may be smaller than theblock data 734 which stores transaction data, however this is not arequirement. The block 730 may store transactional information of Ntransactions (e.g., 100, 500, 1000, 2000, 3000, etc.) within the blockdata 734. According to various embodiments, each transaction may includereliability information 735 within the block data 734 that is added bythe ordering node 710. The reliability information 735 may be different(or a modification of) previously stored reliability information that isprovided by the submitting node.

The block 730 may also include a link to a previous block (e.g., on theblockchain 722 in FIG. 7A) within the block header 732. In particular,the block header 732 may include a hash of a previous block's header.The block header 732 may also include a unique block number, a hash ofthe block data 734 of the current block 730, and the like. The blocknumber of the block 730 may be unique and assigned in anincremental/sequential order starting from zero. The first block in theblockchain may be referred to as a genesis block which includesinformation about the blockchain, its members, the data stored therein,etc.

The block data 734 may store transactional information of eachtransaction that is recorded within the block 730. For example, thetransaction data stored within block data 734 may include one or more ofa type of the transaction, a version, a timestamp (e.g., finalcalculated timestamp, etc.), a channel ID of the distributed ledger 720,a transaction ID, an epoch, a payload visibility, a chaincode path(deploy tx), a chaincode name, a chaincode version, input (chaincode andfunctions), a client (creator) identify such as a public key andcertificate, a signature of the client, identities of endorsers,endorser signatures, a proposal hash, chaincode events, response status,namespace, a read set (list of key and version read by the transaction,etc.), a write set (list of key and value, etc.), a start key, an endkey, a list of keys, a Merkel tree query summary, and the like. Thetransaction data may be stored for each of the N transactions.

According to various embodiments, the block data 734 section of block730 may store information about modifications, updates, deletes,additions, or other changes to a reliability value of an external datasource within reliability information 735. The reliability information735 may include a category type of the external data, a reliabilityvalue (e.g., −1.0 to 1.0, etc.), a timestamp, an identity of theexternal data source, an identification of the change in the reliabilityvalue, and the like.

The block metadata 736 may store multiple fields of metadata (e.g., as abyte array, etc.). Metadata fields may include signature on blockcreation, a reference to a last configuration block, a transactionfilter identifying valid and invalid transactions within the block, lastoffset persisted of an ordering service that ordered the block, and thelike. The signature, the last configuration block, and the orderermetadata may be added by the ordering service 710. Meanwhile, acommitting node of the block (such as blockchain node 712) may addvalidity/invalidity information based on an endorsement policy,verification of read/write sets, and the like. The transaction filtermay include a byte array of a size equal to the number of transactionsin the block data 734 and a validation code identifying whether atransaction was valid/invalid.

The above embodiments may be implemented in hardware, in a computerprogram executed by a processor, in firmware, or in a combination of theabove. A computer program may be embodied on a computer readable medium,such as a storage medium. For example, a computer program may reside inrandom access memory (“RAM”), flash memory, read-only memory (“ROM”),erasable programmable read-only memory (“EPROM”), electrically erasableprogrammable read-only memory (“EEPROM”), registers, hard disk, aremovable disk, a compact disk read-only memory (“CD-ROM”), or any otherform of storage medium known in the art.

An exemplary storage medium may be coupled to the processor such thatthe processor may read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anapplication specific integrated circuit (“ASIC”). In the alternative,the processor and the storage medium may reside as discrete components.For example, FIG. 8 illustrates an example computer system architecture800, which may represent or be integrated in any of the above-describedcomponents, etc.

FIG. 8 is not intended to suggest any limitation as to the scope of useor functionality of embodiments of the application described herein.Regardless, the computing node 800 is capable of being implementedand/or performing any of the functionality set forth hereinabove. Forexample, the computing node 800 may perform any of the methods 510-560shown and described with respect to FIGS. 5A-5F.

In computing node 800 there is a computer system/server 802, which isoperational with numerous other general purpose or special purposecomputing system environments or configurations. Examples of well-knowncomputing systems, environments, and/or configurations that may besuitable for use with computer system/server 802 include, but are notlimited to, personal computer systems, server computer systems, thinclients, thick clients, hand-held or laptop devices, multiprocessorsystems, microprocessor-based systems, set top boxes, programmableconsumer electronics, network PCs, minicomputer systems, mainframecomputer systems, and distributed cloud computing environments thatinclude any of the above systems or devices, and the like.

Computer system/server 802 may be described in the general context ofcomputer system-executable instructions, such as program modules, beingexecuted by a computer system. Generally, program modules may includeroutines, programs, objects, components, logic, data structures, and soon that perform particular tasks or implement particular abstract datatypes. Computer system/server 802 may be practiced in distributed cloudcomputing environments where tasks are performed by remote processingdevices that are linked through a communications network. In adistributed cloud computing environment, program modules may be locatedin both local and remote computer system storage media including memorystorage devices.

As shown in FIG. 8, computer system/server 802 in cloud computing node800 is shown in the form of a general-purpose computing device. Thecomponents of computer system/server 802 may include, but are notlimited to, one or more processors or processing units 804, a systemmemory 806, and a bus that couples various system components includingsystem memory 806 to processor 804.

The bus represents one or more of any of several types of busstructures, including a memory bus or memory controller, a peripheralbus, an accelerated graphics port, and a processor or local bus usingany of a variety of bus architectures. By way of example, and notlimitation, such architectures include Industry Standard Architecture(ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA)bus, Video Electronics Standards Association (VESA) local bus, andPeripheral Component Interconnects (PCI) bus.

Computer system/server 802 typically includes a variety of computersystem readable media. Such media may be any available media that isaccessible by computer system/server 802, and it includes both volatileand non-volatile media, removable and non-removable media. System memory806, in one embodiment, implements the flow diagrams of the otherfigures. The system memory 806 can include computer system readablemedia in the form of volatile memory, such as random-access memory (RAM)810 and/or cache memory 812. Computer system/server 802 may furtherinclude other removable/non-removable, volatile/non-volatile computersystem storage media. By way of example only, storage system 814 can beprovided for reading from and writing to a non-removable, non-volatilemagnetic media (not shown and typically called a “hard drive”). Althoughnot shown, a magnetic disk drive for reading from and writing to aremovable, non-volatile magnetic disk (e.g., a “floppy disk”), and anoptical disk drive for reading from or writing to a removable,non-volatile optical disk such as a CD-ROM, DVD-ROM or other opticalmedia can be provided. In such instances, each can be connected to thebus by one or more data media interfaces. As will be further depictedand described below, memory 806 may include at least one program producthaving a set (e.g., at least one) of program modules that are configuredto carry out the functions of various embodiments of the application.

Program/utility 816, having a set (at least one) of program modules 818,may be stored in memory 806 by way of example, and not limitation, aswell as an operating system, one or more application programs, otherprogram modules, and program data. Each of the operating system, one ormore application programs, other program modules, and program data orsome combination thereof, may include an implementation of a networkingenvironment. Program modules 818 generally carry out the functionsand/or methodologies of various embodiments of the application asdescribed herein.

As will be appreciated by one skilled in the art, aspects of the presentapplication may be embodied as a system, method, or computer programproduct. Accordingly, aspects of the present application may take theform of an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present application may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Computer system/server 802 may also communicate with one or moreexternal devices 820 such as a keyboard, a pointing device, a display822, etc.; one or more devices that enable a user to interact withcomputer system/server 802; and/or any devices (e.g., network card,modem, etc.) that enable computer system/server 802 to communicate withone or more other computing devices. Such communication can occur viaI/O interfaces 824. Still yet, computer system/server 802 cancommunicate with one or more networks such as a local area network(LAN), a general wide area network (WAN), and/or a public network (e.g.,the Internet) via network adapter 826. As depicted, network adapter 826communicates with the other components of computer system/server 802 viaa bus. It should be understood that although not shown, other hardwareand/or software components could be used in conjunction with computersystem/server 802. Examples, include, but are not limited to: microcode,device drivers, redundant processing units, external disk drive arrays,RAID systems, tape drives, and data archival storage systems, etc.

Although an exemplary embodiment of at least one of a system, method,and non-transitory computer readable medium has been illustrated in theaccompanied drawings and described in the foregoing detaileddescription, it will be understood that the application is not limitedto the embodiments disclosed, but is capable of numerous rearrangements,modifications, and substitutions as set forth and defined by thefollowing claims. For example, the capabilities of the system of thevarious figures can be performed by one or more of the modules orcomponents described herein or in a distributed architecture and mayinclude a transmitter, receiver or pair of both. For example, all orpart of the functionality performed by the individual modules, may beperformed by one or more of these modules. Further, the functionalitydescribed herein may be performed at various times and in relation tovarious events, internal or external to the modules or components. Also,the information sent between various modules can be sent between themodules via at least one of: a data network, the Internet, a voicenetwork, an Internet Protocol network, a wireless device, a wired deviceand/or via plurality of protocols. Also, the messages sent or receivedby any of the modules may be sent or received directly and/or via one ormore of the other modules.

One skilled in the art will appreciate that a “system” could be embodiedas a personal computer, a server, a console, a personal digitalassistant (PDA), a cell phone, a tablet computing device, a smartphoneor any other suitable computing device, or combination of devices.Presenting the above-described functions as being performed by a“system” is not intended to limit the scope of the present applicationin any way but is intended to provide one example of many embodiments.Indeed, methods, systems and apparatuses disclosed herein may beimplemented in localized and distributed forms consistent with computingtechnology.

It should be noted that some of the system features described in thisspecification have been presented as modules, in order to moreparticularly emphasize their implementation independence. For example, amodule may be implemented as a hardware circuit comprising custom verylarge-scale integration (VLSI) circuits or gate arrays, off-the-shelfsemiconductors such as logic chips, transistors, or other discretecomponents. A module may also be implemented in programmable hardwaredevices such as field programmable gate arrays, programmable arraylogic, programmable logic devices, graphics processing units, or thelike.

A module may also be at least partially implemented in software forexecution by various types of processors. An identified unit ofexecutable code may, for instance, comprise one or more physical orlogical blocks of computer instructions that may, for instance, beorganized as an object, procedure, or function. Nevertheless, theexecutables of an identified module need not be physically locatedtogether but may comprise disparate instructions stored in differentlocations which, when joined logically together, comprise the module andachieve the stated purpose for the module. Further, modules may bestored on a computer-readable medium, which may be, for instance, a harddisk drive, flash device, random access memory (RAM), tape, or any othersuch medium used to store data.

Indeed, a module of executable code could be a single instruction, ormany instructions, and may even be distributed over several differentcode segments, among different programs, and across several memorydevices. Similarly, operational data may be identified and illustratedherein within modules and may be embodied in any suitable form andorganized within any suitable type of data structure. The operationaldata may be collected as a single data set or may be distributed overdifferent locations including over different storage devices, and mayexist, at least partially, merely as electronic signals on a system ornetwork.

It will be readily understood that the components of the application, asgenerally described and illustrated in the figures herein, may bearranged and designed in a wide variety of different configurations.Thus, the detailed description of the embodiments is not intended tolimit the scope of the application as claimed but is merelyrepresentative of selected embodiments of the application.

One having ordinary skill in the art will readily understand that theabove may be practiced with steps in a different order, and/or withhardware elements in configurations that are different than those whichare disclosed. Therefore, although the application has been describedbased upon these preferred embodiments, it would be apparent to those ofskill in the art that certain modifications, variations, and alternativeconstructions would be apparent.

While preferred embodiments of the present application have beendescribed, it is to be understood that the embodiments described areillustrative only and the scope of the application is to be definedsolely by the appended claims when considered with a full range ofequivalents and modifications (e.g., protocols, hardware devices,software platforms etc.) thereto.

What is claimed is:
 1. A computing system comprising: a processorconfigured to: identify a sequence of nodes in a tree structure based onreferences that correspond to a sequence of off-chain data sources thatdepend from an off-chain data source; determine a reliability value ofthe off-chain data source based on reliability values assigned to thesequence of nodes in the tree structure; and transmit the reliabilityvalue.
 2. The computing system of claim 1, wherein the processor isconfigured to control a network interface to transmit an identifier ofthe reliability value and an identifier of a category type of theoff-chain data source to the client.
 3. The computing system of claim 1,wherein the processor is configured to retrieve the reliability value ofthe off-chain data source from a key value store (KVS) of a statedatabase on a distributed ledger.
 4. The computing system of claim 1,wherein the processor is configured to identify a database entryassociated with the off-chain data source from among a plurality ofdatabase entries associated with the off-chain data source thatcorresponds to a plurality of category types.
 5. The computing system ofclaim 1, wherein the reliability value indicates a level of trustassociated with one or more of the off-chain data source and a dataelement provided from the off-chain data source.
 6. A method comprising:identifying a sequence of nodes in a tree structure based on referencesthat correspond to a sequence of off-chain data sources that\depend froman off-chain data source; determining a reliability value of theoff-chain data source based on reliability values assigned to thesequence of nodes in the tree structure; and transmitting thereliability value.
 7. The method of claim 6, wherein the transmittingcomprises transmitting an identifier of the reliability value and anidentifier of a category type of the off-chain data source.
 8. Themethod of claim 6, comprising retrieving the reliability value of theoff-chain data source from a key value store (KVS) of a state databaseon a distributed ledger.
 9. The method of claim 6, comprisingidentifying a database entry associated with the off-chain data sourcefrom among a plurality of database entries associated with the off-chaindata source corresponding to a plurality of category types.
 10. Themethod of claim 6, wherein the reliability value indicates a level oftrust associated with one or more of the off-chain data source and adata element provided from the off-chain data source.
 11. A computingsystem comprising: a processor configured to: determine whether anagreement on the reliability value of the off-chain data source has beenreached among a plurality of blockchain peers, and, in response to adetermination that the agreement has been reached, store a databaseentry which includes an identity of the off-chain data source and thereliability value within a node of a tree structure within a reliabilitydatabase on a distributed ledger replicated among the plurality ofblockchain peers, wherein the node is stored at an end of a sequence ofnodes in the tree structure that correspond to a recursive sequence ofoff-chain data sources from which the off-chain data source depends. 12.The computing system of claim 11, wherein the off-chain data sourcecomprises one or more of stock data, insurance data, medical data,appraisal data, financial data, and weather data.
 13. The computingsystem of claim 11, wherein the reliability database is implementedwithin a key value store (KVS) of a state database on the distributedledger.
 14. The computing system of claim 11, wherein the reliabilityvalue indicates a level of trust associated with one or more of theoff-chain data source and a data element provided from the off-chaindata source.
 15. The computing system of claim 11, wherein the agreedupon reliability value is a different reliability value than thereceived reliability value.
 16. The computing system of claim 11,wherein the off-chain data source comprises a system that is not allowedaccess to the distributed ledger.
 17. The computing system of claim 11,wherein if the reliability value comprises an updated reliability value,the processor controls a network interface to transmit the updatedreliability value to one or more clients to inform them of the updatedreliability value.
 18. A method comprising: determining whether anagreement on a reliability value of an off-chain data source has beenreached among a plurality of blockchain peers; and in response to adetermination that the agreement has been reached, storing a databaseentry which includes an identity of the off-chain data source and thereliability value within a node of a tree structure within a reliabilitydatabase on a distributed ledger replicated among the plurality ofblockchain peers, wherein the node is stored at an end of a sequence ofnodes in the tree structure that correspond to a recursive sequence ofoff-chain data sources from which the off-chain data source depends. 19.The method of claim 18, wherein the off-chain data source comprises oneor more of stock data, insurance data, medical data, appraisal data,financial data, and weather data.
 20. The method of claim 18, whereinthe reliability database is implemented within a key value store (KVS)of a state database on the distributed ledger.
 21. The method of claim18, wherein the reliability value indicates a level of trust associatedwith one or more of the off-chain data source and a data elementprovided from the off-chain data source.
 22. The method of claim 18,wherein the determining comprises determining that a differentreliability value than the received reliability value is agreed upon.23. The method of claim 18, wherein the off-chain data source comprisesa system that is not allowed access to the distributed ledger.
 24. Themethod of claim 18, wherein if the reliability value comprises anupdated reliability value, transmitting the updated reliability value toone or more clients to inform them of the updated reliability value. 25.A non-transitory computer readable medium comprising instructions, thatwhen read by a processor, cause the processor to perform a methodcomprising: determining whether an agreement on a reliability value ofan off-chain data source has been reached among a plurality ofblockchain peers; and in response to a determination that the agreementhas been reached, storing a database entry which includes an identity ofthe off-chain data source and the reliability value within a node of atree structure within a reliability database on a distributed ledgerreplicated among the plurality of blockchain peers, wherein the node isstored at an end of a sequence of nodes in the tree structure whichcorrespond to a recursive sequence of off-chain data sources from whichthe off-chain data source depends.